The US capital will be Cathay Pacific’s seventh American destination and the 12th-longest route in the world, according to air data firm OAG Aviation.

New direct, ultra-long-haul flights would also ease Hong Kong International Airport’s – and Cathay Pacific’s – reliance on transfer passengers, according to Polytechnic University aviation professor Achim Czerny. Air tickets are traditionally heavily discounted to lure passengers to stop over in the city, instead of taking a direct flight to their final destination.

“There is strong competition between hubs, which reduces yields,” Czerny said.

“I believe that, given the improvements in aircraft technologies, establishing long-haul non-stop flights is a good opportunity for airlines such as Cathay Pacific to serve markets with higher yield potential.”

Hong Kong’s airport is at capacity and will not get its third runway until 2024 at the earliest. And that scarcity of take-off and landing slots raises the stakes for airline bosses, Czerny said.

Cathay Pacific’s new route should help it push back against a new line of ultra-long-haul flights which threaten to take its customers away, by taking people direct when they would otherwise have transited through Hong Kong.

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Qantas Airways recently dealt a blow to hub airports like Hong Kong’s, which rely on transfer passengers, unveiling Perth-London flights. The 14,498km, 17-hour flight saved passengers about three hours on a connecting Perth-Hong Kong-London service. Qantas has ambitions to go even longer, with Sydney-London flights.

And Singapore Airlines recently started flying from Singapore to San Francisco non-stop, which comes in at 13,593km and 17 hours 15 minutes. The carrier still runs its Singapore-Hong Kong-San Francisco service.

The newer ultra-long-haul flights have been made possible by the fuel-efficient Airbus A350 – which has a maximum range of 15,000km – and the Boeing 787, which can fly 14,140km.

An even longer-range A350 aircraft, capable of 18,000km in one go, is set to take flight next year. Singapore Airlines intends to use that plane to grab the “longest flight in the world” title, restarting non-stop flights from the city state to New York, signalling a return for flights of more than 18 hours. The carrier axed the non-stop New York flights in 2003, when high fuel prices made them uneconomical.

The longest distance currently covered by a commercial flight is the 14,535km between Auckland and Doha, plied by Qatar Airways.

“With a competitive market thanks to the fast-growing Middle East and [mainland] Chinese airlines, now is the time for carriers to launch these new, ultra-long-haul routes, to be able to offer unique non-stop services,” Ellis Taylor, Asia finance editor at industry publication Flight Global, said.

He said he expected Cathay Pacific to open up more similarly long routes to blunt the competition. Miami and Mexico City are two ultra-long-haul destinations seen as attractive to Cathay Pacific, and could be reached from Hong Kong by more advanced aircraft.

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Cathay Pacific’s Washington flight is expected to launch in September next year. To begin with it will not be a daily service, but a source said bosses hoped demand would grow to sustain one flight per day.

Flights to the US capital are expected to take off from Hong Kong in the late afternoon or early evening, arriving in Dulles Airport at night. Flights in the opposite direction will be at night, ensuring an early morning landing in Hong Kong to lure passengers heading onwards to mainland China and Southeast Asia.